China and the United States are nearing the end of negotiations over a key agreement aimed at increasing trade between the two nations, former Chinese minister of commerce Chen Deming reportedly said Wednesday. The Bilateral Investment Treaty (BIT) has been in the works for several years now, and, last September, the two countries reaffirmed that finalizing the accord was a “top economic priority.”

“After years of negotiations, most of the core issues have been resolved, and the negative list is the only thing left to be settled,” Chen, speaking on the sidelines of a conference in Boao, China, reportedly said.

The negative list spells out the industries and sectors in which foreigners are barred from investing. Even the Shanghai Free Trade Zone, seen as a testing ground for future economic and social reforms, includes a lengthy list of off-limit industries, ranging from agriculture to automobile manufacturing.

Although more than 20 rounds of talks over the BIT have been held since negotiations first began in 2008, the composition of the negative list has remained a key sticking point. In September, during talks conducted on the sidelines of Chinese President Xi Jinping's trip to Washington, senior U.S. officials claimed that they were able to get Beijing to shrink the list of sectors it is seeking to exclude from the framework.

“In light of the progress made in the BIT negotiations and both sides’ improved negative list proposals ... the United States and China commit to intensify the negotiations and to work expeditiously to conclude the negotiation of a mutually beneficial treaty that meets these high standards,” the White House said in a statement released in September.

On Wednesday, Chen also reiterated comments made last week by the Chinese Premier Li Keqiang, when he said that opening domestic markets to foreign investors should be a “reciprocal” process.

“The U.S. should also be more open to China, not only in terms of market access, but also in the review aspect where more transparency is needed,” Chen reportedly said. “No matter who becomes the [next] U.S. president, when he or she takes office, he must see the U.S. will have to be more open to the world, otherwise U.S. companies and people will be affected.”

With bilateral trade reaching nearly $600 billion in 2015, China is currently America’s largest trading partner. The BIT is being seen by many as a stepping stone toward a future free-trade agreement.

While the Chinese government hopes that greater foreign competition and investment would reinvigorate its slowing economy, U.S. investors believe that the treaty will give them increased access to China's many state-dominated industries, including financial services and telecommunications.